package serviet;

import pojo.User;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

@WebServlet(urlPatterns ={ "/user"})
public class  Userserviet extends HttpServlet {
    // ait+insert

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        List<User> users =new ArrayList<>();
        //jdbc操作数据库 查询
//1.加载驱动
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");

            //2.获取链接(url username password)
            String url = "jdbc:mysql://127.0.0.1:3306/jdbc?characterEncoding=utf-8";
            Connection connection = DriverManager.getConnection(url, "root", "319257rj");
            //if (connection != null) {
            //    System.out.println("连接成功");
            //}
            //3.写sql语句
            String sql = "select * from user";
            //4.预编译sql
            PreparedStatement preparedStatement = connection.prepareStatement(sql);
            //5.如果有参数设置参数

            //6.执行sql语句
            ResultSet resultSet = preparedStatement.executeQuery();
            //7.遍历结果集
            while (resultSet.next()) {
                User user = new User();
                user.setId(resultSet.getInt(1));
                user.setName(resultSet.getString(2));
                user.setPassword(resultSet.getString(3));
                users.add(user);

            }
            //8.关闭资源
            resultSet.close();
            preparedStatement.close();
            connection.close();
            //把集合中数据存储到作用域中
            req.setAttribute("users",users);
            //打开界面
            req.getRequestDispatcher("user.jsp").forward(req,resp);

        } catch (ClassNotFoundException e) {
            throw new RuntimeException(e);
        }catch (SQLException e) {
            throw new RuntimeException(e);
        }
    }

    }





